Beri, Akash (2010)
M.Res. thesis, University of Birmingham.
The objective of this project is to fabricate a surface that is optimally spaced and well-defined, with respect to the molecular components to enable efficient binding from the surface. This binding will be done using supramolecular interactions and the steric bulk of dendrons (to achieve the spacing). In order to do this, the axle component of a pseudorotaxane complex would have to be synthesised and absorbed to the surface via covalent bonding (chemisorption) to create a self-assembled monolayer (SAM). This is spaced out by the steric bulk of the dendrons which is attached to the wheel component of the pseudorotaxane complex, that is hydrogen bonded to the axle. The pseudorotaxane complex will then disassemble by pH modulation leaving behind spatially separated chemisorbed axle components and simultaneously the vacant surface space will be filled with tri ethyelene glycol thiol terminated alkane thiol (TEGT) creating an optimally spaced SAM. The first part of this research involved the synthesis of a crown ether (the wheel component) covalently attached to a bulky dendron (Scheme 3.3, compound 12). Successful synthesis was achieved over a five step procedure, allowing the complexation part of the research to take place. The next part of the research involved the complexation of dibenzo  crown 8 (DB24C8) with a dialkylammonium thiol, 1, and the complexation of 12 with a dialkylammonium thiol, 1, to form pseudorotaxane like complexes. Both complexation reactions were completed, indicated by the 1H NMR showing both the pseudorotaxane complex and the starting materials. Therefore, further work is required in the complexation step, as any uncomplexed dialkylammonium thiol, 1, will have an effect on the spacing of the SAM. SAM formation of the single components (1 and triethylene glycol, 2) involved in the mixed monolayer were monitored and characterised over a 24 hour time period by a combination of contact angle, ellipsometry and X-ray photoelectron spectroscopy (XPS). Results indicate that for both components higher molecular ordering was achieved when the immersion time was 24 hours. During the research two control studies were conducted on gold (Au) surfaces and were characterised by contact angle and ellipsometry. Results indicate that 12 had no major affinity to Au surfaces and that TEGT, 2, can displace a fully formed dialkylammonium thiol, 1, SAM. Further work is required to confirm that there is zero affinity between 12 and Au surface and to find out to what extent the TEGT displaces the dialkylammonium thiol.
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